The American Welding Society specifications AWS A5.20/A5.20M and AWS A5.36/A5.36M, and other similar global specifications, govern the technical requirements for flux cored electrodes designed for welding carbon steels. For gas-shielded flux cored carbon steel electrodes classified as E7XT-1C, E7XT-1M, E7XT-9C, E7XT-9M, E7XT-12C, and E7XT-12M and containing titanium dioxide (TiO2) based slag systems, AWS A5.20/A5.20M and AWS A5.36/A5.36M require the alloy content in the weld metal to be no greater than 175% manganese (1.60% for E7XT-12 type), 0.12% carbon, 0.90% silicon, 0.20% chromium, 0.50% nickel, 0.30% molybdenum, 0.08% vanadium, and 0.35% copper Although nickel is beneficial to weld metal toughness and ductility properties, the maximum allowed nickel level in these electrode types is fairly restrictive. Therefore, carbon, manganese, molybdenum, and silicon levels typically are adjusted to optimize weld metal properties.
In general, conventional gas-shielded flux cored welding electrodes with titanium dioxide based slag systems include significant levels of manganese and also may include small concentrations of boron to achieve desired weld metal toughness, tensile, and ductility properties. A drawback of conventional gas-shielded flux cored electrodes including titanium dioxide based slag systems is that the significant manganese levels that these electrodes contain may not meet certain emissions control regulations. For example, Metal Fabrication Hazardous Air Pollutants (MFHAP) requirements under U.S. Environmental Protection Agency regulations at 40 CFR Part 63 Subpart which recently became effective, limit the manganese content of certain welding electrodes to less than 1.0 weight percent, based on total electrode weight.
The objectives of the present disclosure are to provide a welding electrode that contains low levels of manganese and yet produces structurally sound weldments.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present application with reference to the drawings.